


The Boy Who Killed

by AedanMaxwell



Series: Random Harry Potter Fics That Are Up For Adoption [3]
Category: Harry Potter - J. K. Rowling
Genre: Assassin!Harry, BAMF!Harry, Dark!Harry, Dumbledore Bashing, Gratuitous titles given to Hrary, I really hate the 'greater good', Mentor!Snape - Freeform, Ron Weasley Bashing, Slytherin!Harry, Smart!Harry, Someone gets dead but no one important, Uhh..., Who's name is actually Arcturus in this, good!Voldemort
Language: English
Status: Completed
Published: 2017-08-24
Updated: 2017-08-24
Packaged: 2018-12-19 08:32:14
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 4,348
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11893941
Author URL: https://archiveofourown.org/users/AedanMaxwell/pseuds/AedanMaxwell
Summary: Harry trained from a young age to become someone who had control over their life, having had none while he was at the Dursleys. So he does the most logical thing, he changes his name to Arcturus Sayre-Black and becomes an assassin by the name of Blaidd.





	The Boy Who Killed

Arcturus had tried his best to lead an unassuming childhood, always hiding in the background, making sure he was never remembered. It was the first rule of an assassin. Make sure you’re always blending in. It helped that he had magic to aid him.

  
Having studied under different assassins - both Muggle and wizard - he was very much in demand in both worlds. His utilization of Muggle weapons as well as the his talent with lethal spells was unique to him alone. Muggles, of course, couldn’t do magic, and Hit Wizards as well as magical assassins thought themselves above such technology and weaponry.

  
Receiving an owl shortly after waking up had brightened what was otherwise going to be a boring day of training and studying. “Hogwarts School of Witchcraft and Wizardry… I’ve been waiting for this.”

 

* * *

  
  
He had discovered, by taking a contract just after his 8th birthday from one Tom Marvolo Riddle, that the Headmaster of the school had the Wizarding world under this thumb, and how his little Order had tried to paint the Dark Lord in a bad light, pinning Dumbledore’s murders for the “Greater Good” on him.

  
Deciding to do a little research himself, Arcturus began to go about Diagon Alley in disguise, hearing whispers about the evil Lord Voldemort, and how a child named Harry Potter had defeated him. Whenever he heard this, the emerald-eyed boy resisted the urge to scoff. Marvolo, as he liked to be called, had gone into hiding because of Dumbledore killing Lily and James Potter, and trying to kill Harry.

  
Arcturus knew his past. He had only lived with the Dursleys as long as he had to until he was sure he could survive on his own. At age seven, having learned about what magic was by conversing with snakes, Harry ran away to Diagon Alley. He made Gringotts his first stop, who were livid with the leader of the Light and were all too willing to help Harry James Potter become Arcturus Hadrian Sayre. He and the goblins had decided to honor his ties to the Black family and chose Arcturus as a first name, as well as the sacrifice his parents made for him by keeping the name Hadrian, though as a middle name. Then he began to make a name for himself as an assassin after he used a little parselmagic to convince an assassin residing in Knockturn Alley to make Arcturus his apprentice.

  
Since he knew he couldn’t have himself being recognized, he had the goblins acquire a charmed silver ring with strong Glamours that turned his eyes an ice blue and got rid of his scar. For when it came time to go to Hogwarts, the Glamours also made him seem underfed and shorter than he actually was, like Dumbledore was expecting.

 

* * *

 

The little assassin always began his day with an hour of meditation in order to clear his mind, suppress his emotions, strengthen his Occlumency shields, and reflect on his plan for the day. Glancing over his letter, he noticed that written on the bottom of his acceptance letter was a short message in spidery but neat handwriting. “I will be collecting you at noon the day you get this letter. -Professor Snape”

 

Knowing the name from his meetings with Marvolo, Arcturus knew the man wouldn’t recognise him because of the mask he wore when with employers, but he still worried. The man was a spy after all.

  
Quickly pulling on dark jeans and a green button-up, Arcturus cursed himself for staying up too late last night studying counter-curses, thanked his luck for still having time to meditate, and had just finished sliding a dagger into his combat boot when there was a knock on the door of the flat he was staying in while the Muggle owners were on vacation.

  
Quickly strapping his wand holster to his left forearm, he cast Disillusionment charms on his weapons and opened the door after checking that it was indeed Snape.  
“Hello, Mr. Sayre. I am Professor Snape, Potions Master at Hogwarts.” The older man spoke with a slight sneer at the end, as if the last place he wanted to be was that school.   
Holding out a hand, the boy bowed slightly, “It’s a pleasure to meet you, Professor. Please, call me Arcturus.”

  
The Potions Master shook his hand firmly and raised an eyebrow after a second. “A young man with manners. We’ll get along well, provided you don’t try and blow up my classroom.”

  
The statement was spoken a bit forcefully, denoting the amount of explosions that have either happened or almost happened during his tenure.   
“I shall endeavor to not blow my cauldron to bits, sir.”

  
Arcturus gave his best disarming and innocent smile, knowing he was a flawless actor, and couldn’t help but feel a flicker of amusement because of the elder wizard.  
Stepping out and closing the door, Arcturus made sure he had all his belongings in his shrunken bag, which was residing in his pocket, and gestured to the elevator, “Shall we, sir?”

  
He let Snape lead him out of the building and into a deserted alley, putting on a confused face. “What are we doing, Professor?”

  
Glancing at him, Snape explained, “We’re going to Apparate to the Leaky Cauldron. Vomit on me and you can do your school shopping by yourself.”

  
Without so much as a warning, Severus grabbed his arm, and with a crack coupled with the feeling of being squeezed into a tube, the pair landed in a dark alley next to the pub. Arcturus thanked the snake that had told him he should learn to Apparate, and made a show of looking queasy. Placing a steadying hand on the wall beside him, the only words of comfort offered were, “The first time is always the worst.”

  
The young wizard knew he would get along with the professor well, and everything he did seemed to solidify that thought in Arcturus’s mind. He instinctively felt for the dagger strapped to his hip, and was glad Snape was momentarily distracted by a stuttering man in a turban. Forcing himself to relax, he let himself be led to the back of the pub to a brick wall. He paid attention to what bricks the man tapped with his wand to open the way to Diagon Alley, having never come this way himself.

  
As the wall split, he put on his awestruck and naive mask and practically bounced into the alley. Turning to Snape, he bounced on his toes in forced excitement, “Where to first, sir?”

  
“Gringotts bank. We need to see of you have any vaults, and if not, take money from the school’s account,” the man explained while gesturing to a grand looking stone building.

They entered, and one of the goblins who Arcturus knew to be Griphook gestured them to his station. “How can I be of service to you today, sirs?”

“I need to know if Mr. Sayre has any vaults.”

  
Griphook looked down at Arcturus, who nodded minutely. He looked to the professor. “Very well. If the two of you would follow me, please.”

  
They were led into a dark back room that held only a table and four chairs. Seating themselves, Griphook conjured a stone bowl covered in runes as well as a knife. “Mr. Sayre, I’m going to need some of your blood. Please hold your hand over the bowl.”

  
Doing as he was instructed, and showing the proper amount of apprehension, he inwardly remembered why he didn’t like being in public. Emotions were exhausting.   
He made a show of flinching when his palm was cut open, and letting out a sigh of relief when the obsidian-eyed spy offered to heal the cut.

The goblin spoke a short incantation, and a list in glowing letters appeared above the bowl.

 

 

**Arcturus Hadrian Sayre**   
**(previously known as: Harry James Potter)**

**Heir to the house of Slytherin**   
**Heir of the house of Gaunt**   
**Heir to the house of Peverell**   
**Heir to the house of Riddle**   
**Lord of the house of Black**   
**Lord of the house of Potter**   
**Lord of the house of Sayre**   
**Lord of the house of Gryffindor**

 

 

Snape sat shocked as the list glowed for them all. Arcturus drew his wand, and spoke softly, “We have two options. One: we perform an Unbreakable Vow, or two: I cast secrecy charms. Your choice, Professor.”

  
“And if I choose neither option?” The man challenged with a borderline arrogant smirk which Arcturus returned.

 

“Then the goblins and I will force you using very painful methods. We have worked too hard to keep this a secret. We can’t have you blowing it to the senile codger.”

  
Nodding, Snape chose, “The second option, granted you can cast them. An Unbreakable Vow leaves marks.”

  
Without saying a word or giving any warning, the assassin cast a set of secrecy charms, some Darker than others. It promised Snape extreme amounts of pain should he manage to reveal something he shouldn’t.

  
Eyes widening at the Dark magic that swirled, Snape began to wonder how much more to this boy there was that he couldn’t see.

  
“Harry Potter had green eyes. I remember the first time Lily let me hold you. They were the same color as hers,” the confused man spoke, even as he internally questioned where the child had learned such dark spells.

  
Taking the ring off of the middle finger of his left hand, Arcturus could see the Professor’s eyes widen at the changes.

  
Sliding the ring back on, he watched the wizard process all the information just given to him. While that happened, Arcturus requested 500 Galleons from the Sayre vault.  
Once the elder was ready to depart, Griphook offered something wrapped in silk to the black-haired boy. “This is a wand crafted by Salazar Slytherin himself. It is made from snakewood with a core of Basilisk horn. We had meant for it to find it’s way to Lord Slytherin, but it seems as though you are just as suited to have it. This wand is said to have an incredible capacity for healing, Mr. Sayre. Use it well.”

  
Bowing to the goblin, he said, “Thank you, sir. May your gold be plentiful and your enemies tremble at your feet.”

  
The teller bowed in return, “The same to you, Mr. Sayre. You will always be welcome here at Gringotts.”

 

* * *

  
Finally exiting the bank, he was backed into a deserted alley by the older man. Resisting the urge to grab a knife, the boy let himself be pushed. “Tell me, why did you not seem surprised when you were handed the wand of Salazar bloody Slytherin?”

  
Backing away, Arcturus smiled knowingly. “It wouldn’t be any fun if I just gave everything away, now would it? You’re a Slytherin, so use that cunning and ambition to figure it out.”

  
Grabbing the Potion Master’s hand and pulling him back into Diagon Alley, Arcturus took his school supply list out of his pocket, heading towards Madam Malkin’s and trusting the professor would follow.

  
The rest of the day passed without incident, and Arcturus began to head towards the Leaky Cauldron, his stomach protesting the lack of food. He was stopped with a hand around his arm. “We still need to go to Ollivanders.”

  
“No we don’t,” the younger responded, glaring at the hand around his arm as he drew his wand out of it’s holster, “Do you not remember me casting those charms earlier?”  
Having the decency to look a bit abashed, Severus nodded as he let go of his charge. Arcturus rolled his eyes, putting away his wand and starting off towards food again.

 

* * *

 

  
After eating his weight in food, amused by his temporary guardian’s look of incredulity, the man offered him a place to stay until school started. “It’s Prince manor. You would be welcome to any books in the library, and the training room, which is stocked with dummies to practice on.”

  
Accepting his offer, they quickly Apparated to the manor, a house elf waiting for them. Snape sent Merry the elf to prepare a guest bedroom, and began to show Arcturus around.

  
After their tour, they parted at the younger’s bedroom. Severus had to report to Albus, and Arcturus was eager to make a dent in the books he had gotten for his first year.

 

* * *

 

Falling asleep on the couch in the library, the spy seemed very amused to find him the next morning surrounded by half-read books with a little drool dried on his face.  
Glad he had had the foresight to change into comfortable clothes and stash his weapons, Arcturus picked up his wand from the floor and yawned.

  
After giving up trying to tame his shoulder-length hair, he finally turned to the wizard, who was once again dressed in his all black robes. Blue eyes met black as he found himself pulled up off the couch and herded to breakfast by a pushy Potion’s Master without so much as a good morning.

  
Later that morning, the 11 year-old was taken to the basement to a secluded Potion’s lab and asked to demonstrate what all he’d learned in his reading last night.  
Quickly brewing an Antidote to Common Poisons, he earned an approving nod from the Professor after he examined it. “It seems you’ll be more than prepared for this year, Arcturus.”

 

* * *

  
  
Arcturus routinely snuck out to carry out contracts, feeling most comfortable with his Accuracy International L96A1 slung over his shoulder, his SIG Sauer P226 at his hip, and his wands in their thigh holsters.

  
He smiled at the thought of the large deposit entering his account, and his smile grew like the pool of blood surrounding his latest victim.  
The employer stood behind him, “Thank you for offering your skills, Blaidd.”

  
Blaidd bowed and, with a glance back at his kill dead on the pavement below their rooftop perch, he Apparated back to Prince manor, right into his room. He stripped as quickly as he could, hiding his clothing and mask in a secret, expanded pocket of his bag, he threw up temporary wards so he’d know if his guardian was coming, and he set about taking his guns apart to clean them.

  
Packing them away afterwards, he got rid of the wards and made sure everything was properly hidden before going to sleep.

 

* * *

  
  
Other than the occasional contract, he quickly made his way through both the first, second, and third year course material in the last month of summer. Soon enough it was time to go to Hogwarts, and even though he protested riding the train, Severus made him.

  
Begrudgingly climbing onto the Hogwarts Express, he quickly made his way to an empty compartment, and planned on napping the entire way. His hopes were quickly dashed when a redheaded boy entered and sat down without asking permission. Opening his eyes, he sent a cold glare to the boy, who held out a hand, “Ron. Ron Weas-”  
He was cut off by the compartment door opening again, and this time a blonde sneered in the ginger’s direction, “You must be a Weasley. The hair and hand-me-down robes is a giveaway.”

  
Ron stood, “And you must be a Malfoy, you blonde prat.”

  
Quickly clearing his throat loud enough to get both their attention, he spoke, “I don’t care about whatever blood feud you two have, just don’t drag me into it. I was napping peacefully when you - Mr. Weasley - barged in here without permission. As for you, Mr. Malfoy. You shouldn’t just barge in specifically to pick a fight. I’m sure, as a proper pureblood, you were raised with more decorum than that.”

  
The blonde nodded at his words, “I apologize. I sometimes forget myself. Thank you….”

“Arcturus Sayre-Black,” he filled in for the boy, shaking the hand extended to him.

“Why the bloody hell would you shake hands with a Malfoy?! They’re Death Eaters, followers of You-Know-Who!”

  
They both turned to the flustered redhead, whose face now matched his hair, and Arcturus pointed to the door, “You and your prejudices can get the fuck out of my compartment, Weasley.”

  
He hadn’t raised his voice, but the deadly-calm tone he used made the boy practically run away.

  
The blonde smirked, “I’m Draco Malfoy, by the way.”

 

* * *

  
  
The two chatted until Draco realised they were approaching the school and they made trips to the bathroom to change into their school robes.

  
When the train stopped, they stepped off and followed the crowd of other first years to where a half-giant was shouting, “Firs’ years! Firs’ years over here!”

  
The man’s hairy face beamed over the sea of heads.

  
“C’mon, follow me - any more firs’ years? Mind yer step, now! Firs’ years follow me!”

  
Arcturus watched in amusement as the rest of the students slipped and stumbled their way down a steep narrow path. Draco had to grab Arcturus’s arm more than once to keep himself upright.

  
Nobody spoke much on the trek, too focused on not falling arse over tea kettle. The path opened up suddenly to the edge of the Black Lake. Perched high atop a high mountain on the other side, its windows sparkling in the starry sky, was Hogwarts, with its many turrets and towers. There was a loud chorus of “Oooooh!”

  
“No more’n four to a boat!” Hagrid called, pointing to a fleet of little boats sitting in the water by the shore.

Arcturus pulled Draco to a boat, and the two were quickly followed by a round-faced boy looking decidedly tearful and a blonde girl who was in her own little world.

  
They all sat down and the boy spoke, “Have either of you seen a toad?”

  
At the shake of their heads he let out a sad sigh. “Oh well. Hello, my name’s Neville Longbottom, and this is Luna Lovegood.”

  
The black-haired boy smiled back, making sure to convey warmth and openness. “Hello, I am Arcturus Sayre and this is Draco Malfoy.”

  
Draco reluctantly shook the boy’s hand, and Luna simply waved at them. Any further conversation was interrupted by Hagrid shouting “FORWARD!”

  
The boats began to glide across the lake, which was as smooth as glass. Everyone was silent, staring up at the great castle overhead. It towered over them as they sailed nearer and nearer to the cliff on which it stood.

  
“Heads down!” yelled Hagrid as the first boats reached the cliff; the rest of the children obediently bent their heads while Arcturus merely flicked his wrist and the ivy curtain parted around his head.

On the other side of the curtain was a wide opening in the cliff face. They were carried along a dark tunnel, which seemed to go right underneath the castle, until they reached a kind of underground harbour, where they climbed out onto the makeshift shore of rocks and pebbles.

  
“Oy, you there! Is this your toad?” said Hagrid who was checking the boats as people climbed out.

  
“Trevor!” cried Neville blissfully, holding out his hands. Then they clambered up a passageway in the rock after Hagrid’s lamp, coming out at last onto smooth, damp grass right in the shadow of the castle.

  
They walked up a flight of stairs, and Slytherin Lord had to contain his disgust at how out of shape his year-mates were. Most of them were huffing and puffing by the time they all crowded around a set of huge, oak front doors.

  
“Everyone here? You there, still got yer toad?”

  
Hagrid raised a gigantic fist and knocked three times, some of the students near Neville began snickering at the embarrassed flush creeping into his cheeks.

  
The door swung open as soon as Hagrid finished knocking, and a tall, rather severe-looking witch greeted them, her emerald-green robes that shimmered slightly in the lamplight. She had a very stern face and Arcturus knew that this must be the Head of Gryffindor that Severus told him about.

  
“The firs’ years, Professor McGonagall,” said Hagrid.

  
“Thank you. I will take them from here.”

  
She pulled the door open all the way. The entrance hall was so big you could have fit a two-story house inside and still have room to walk comfortably. A magnificent marble staircase facing them led to the upper floors.

  
As soon as he stepped foot in the castle he felt the tingle of Hogwart’s magic greeting him like an old friend. He supposed it must be because he was the Gryffindor Lord and Slytherin heir. The magic recognised his blood.

  
They followed Professor McGonagall across the flagged stone floor. Arcturus could hear the racket of hundreds of voices from a doorway to his right, which he assumed was the Great Hall. Showing them into a small, empty chamber, the severe-looking Professor ushered them in. They all barely fit inside, and the blue-eyed wizard had to resort to throwing death glares at anyone who dared to so much as brush against him. Pretending he had an itch, he felt for the dagger in his boot, just for the peace of mind that it was there.

  
“Welcome to Hogwarts,” said Professor McGonagall. “The start-of-term banquet will begin shortly, but before you take your seats in the Great Hall, you will be sorted into your houses. The Sorting is a very important ceremony because, while you are here, your house will be something like your family within Hogwarts. You will have classes....”

  
Tuning her out, Arcturus took the opportunity to look around at his classmates. The Weasley boy was still sending him what the boy no doubt thought was an impressive glare, but in reality left him looking rather constipated. Neville was stroking Trevor’s back while listening to the Professor, and Luna was smiling dreamily at the wall. Draco was looking decidedly bored as he yawned and subtly flipped Ron the bird. The boy turned an interesting shade of red, approaching purple, and the boy waited until the door was closed as the Professor left to exclaim, “What was that for, you bloody prat?!”

  
Draco put on an offended face and held a hand to his chest. “I’m sure I have no idea what you’re prattling on about, Weasel.”

  
Wandlessly murmuring a stinging hex, it hit Ron’s ear, and he swore loudly just as McGonagall was entering the room again. She sent the boy a scalding glare, and he had the decency to look ashamed. “Move along now, the Sorting Ceremony is about to start.”

 

She looked over all of them before speaking in a sharp voice, “Now, form a line and follow me.”

  
They all quickly lined up, not wanting to vex the woman further, and were led through a pair of double doors into the Great Hall.

 

Arcturus looked around at all the thousands of candles that were floating in midair over four long tables, where the rest of the students were sitting. The tables were laid with glittering golden plates and goblets. At the top of the hall was another long table where the teachers were sitting. Spotting Snape, the man met his eyes for a moment and offered him the barest of smiles that passed so quickly that they were both sure no one else saw it.

 

Professor McGonagall led the first years up to the table, so they stood facing the students, backs to the professors. Glancing up to the ceiling, he felt calmed by the swirling stars and galaxies that graced the enchanted surface. Then he turned to the pointed wizard’s hat that was sitting on a four-legged stool. It was patched, frayed, and extremely dirty. Said hat gave a twitch before a tear near the brim opened and the hat began to sing.

  
Feeling the urge to sneer at how cliche everything was, he felt prodding at his Occlumency shields, almost like a polite knock, and he let the Potion’s Master into his head. Snape had told him that two people who had mastered the Mind Arts could speak to each other. He heard the Professor’s voice softly in his head, _Cause any trouble yet?_

  
 _Only a small stinging hex on the latest Weasley_. Arcturus responded mentally.

  
 _How did I know you would be trouble before the year even started?_ Snape growled, not actually angry, just speaking that way out of habit.

  
_You know he started it, so knock it off unless you want to find yourself at the end of one of my nastier hexes, Severus._

  
He could almost picture the smirk the man would be sporting if they were speaking privately. Both knew they would probably never find another person to match their brand of threatening banter. Neither actually meant the threats, but it was how each told the other they cared. The two had grown close, sharing a mutual hate of Dumbledore, an affinity for the Dark Arts, and an insatiable want to learn all that there was to learn.

  
Passing the time by listing all the spells he knew in alphabetical order, he kept tabs on the three he was interested in, Neville and Luna both got Sorted into Ravenclaw, and Draco into Slytherin. He stepped up when his name was called, and as soon as the hat touched his head, he felt prodding at his Occlumency shields. He let the hat in, and heard, _Ah, Mr. Potter. I had wondered when I might be seeing you. You would do well in any house, but with your occupation, I think Slytherin would fit best._

  
_Please, sir, call me Arcturus. I believe Slytherin would be a good fit as well._

  
The hat called out, “SLYTHERIN!”

  
He walked to sit next to Draco, and waited to see how Weasley would be placed. Finally his name was called, and the hat had barely touched the nervous boy’s head when it called out, “HUFFLEPUFF!”

  
The Great Hall quieted instantly. Walking begrudgingly to his table, the redhead looked like he wanted to shout and curse and tell the hat how wrong it was, but he managed to contain himself. Blaise Zabini was the last to be Sorted, and he went to Slytherin.

  
Occupied by his own thoughts, he barely noticed the food that appeared before them. 


End file.
